Reverse lookup for classless networks

[John Levine]

From: John Levine <johnl at iecc.com>
To: bind-users at lists.isc.org
Subject: Re: Reverse lookup for classless networks
In-Reply-To: <mailman.76.1545933824.716.bind-users at lists.isc.org>
Organization: Taughannock Networks
Cc: gtaylor at tnetconsulting.net
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In article <mailman.76.1545933824.716.bind-users at lists.isc.org> you write:
>1)  The parent zone needs to have the delegation like Barry depicted above.
>2)  The child zone needs to have records for the name being looked up. 
>Nothing specifically translates to them needing to be in separate zones.

Well, there's those pesky old DNS standards, but we're used to software
working around screwed up zones.

If the parent delegates a name to a child server, the child server
must have an SOA at that name, along with whatever else you might
want to put there.  BIND will generally forgive what you're doing,
but I wouldn't expect it to work on other name server software.

>I could easily create a zone like this:
>
>; 1.0.192.in-addr.arpa.zone on local nameservers ns{1,2}.yourdomain.com
>$ORIGIN 1.0.192.in-addr.arpa.
>0   IN PTR web.yourdomain.com.
>1   IN PTR ftp.yourdomain.com.
>...
>128 IN NS  ns1.parent.example.
>     IN NS  ns2.parent.example.
>129 IN NS  ns1.parent.example.
>     IN NS  ns2.parent.example.
>...

>In essence, you end up with two independent zones for the same domain 
>name, 1.0.192.in-addr.arpa, cross delegating /different/ records to each 
>other.  Thus, both are perfectly happy to answer authoritatively with 
>PTR records for the IPs that they are ""responsible for, while 
>""delegating (redirecting) to the other name servers for the IPs that 
>they aren't locally responsible for.

I see a delegation loop.   What's the lookup chain supposed to be
for 128.0.192.in-addr.arpa?

R's,
John

PS: What's wrong with using $GENERATE in the parent zone like everyone
else who uses BIND does?